One of the major questions being pursued in developmental biology today is, "How are specific genes turned on and off at the appropriated times in a developmental sequence?" The ultimate goal of the research contained in this proposal is to study the processes of differentiation in the life cycle of the dimorphic bacterium Caulobacter crescentus and to attempt to understand the modes of regulation controlling these processes. Work carried out in our laboratory so far has resulted in the development of techniques for the genetic analysis of C. crescentus, the isolation of mutants, the construction of a genetic map and the construction of a clone bank of C. crescentus genes. These results are being used in our laboratory and elsewhere to study specific C. crescentus genes, but more work is needed to maximize the potential for the use of genetic tools to study the temperal control of gene regulation in C. crescentus. Therefore, we propose: 1) To refine and improve the C. crescentus genetic map: a) by precise mapping of areas of uncertainty and; b) by mapping of additional genes. 2) To develop new vectors for transposon mutagenesis. 3) To establish the circularity of the C. crescentus chromosome. 4) To perform fine structure analysis of specific regions of the C. crescentus chromosome.